1 files changed, 405 insertions, 0 deletions
diff --git a/src/net/http/fcgi/child.go b/src/net/http/fcgi/child.go
new file mode 100644
index 0000000..756722b
--- /dev/null
+++ b/src/net/http/fcgi/child.go
@@ -0,0 +1,405 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package fcgi
+
+// This file implements FastCGI from the perspective of a child process.
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"io"
+	"net"
+	"net/http"
+	"net/http/cgi"
+	"os"
+	"strings"
+	"sync"
+	"time"
+)
+
+// request holds the state for an in-progress request. As soon as it's complete,
+// it's converted to an http.Request.
+type request struct {
+	pw        *io.PipeWriter
+	reqId     uint16
+	params    map[string]string
+	buf       [1024]byte
+	rawParams []byte
+	keepConn  bool
+}
+
+// envVarsContextKey uniquely identifies a mapping of CGI
+// environment variables to their values in a request context
+type envVarsContextKey struct{}
+
+func newRequest(reqId uint16, flags uint8) *request {
+	r := &request{
+		reqId:    reqId,
+		params:   map[string]string{},
+		keepConn: flags&flagKeepConn != 0,
+	}
+	r.rawParams = r.buf[:0]
+	return r
+}
+
+// parseParams reads an encoded []byte into Params.
+func (r *request) parseParams() {
+	text := r.rawParams
+	r.rawParams = nil
+	for len(text) > 0 {
+		keyLen, n := readSize(text)
+		if n == 0 {
+			return
+		}
+		text = text[n:]
+		valLen, n := readSize(text)
+		if n == 0 {
+			return
+		}
+		text = text[n:]
+		if int(keyLen)+int(valLen) > len(text) {
+			return
+		}
+		key := readString(text, keyLen)
+		text = text[keyLen:]
+		val := readString(text, valLen)
+		text = text[valLen:]
+		r.params[key] = val
+	}
+}
+
+// response implements http.ResponseWriter.
+type response struct {
+	req            *request
+	header         http.Header
+	code           int
+	wroteHeader    bool
+	wroteCGIHeader bool
+	w              *bufWriter
+}
+
+func newResponse(c *child, req *request) *response {
+	return &response{
+		req:    req,
+		header: http.Header{},
+		w:      newWriter(c.conn, typeStdout, req.reqId),
+	}
+}
+
+func (r *response) Header() http.Header {
+	return r.header
+}
+
+func (r *response) Write(p []byte) (n int, err error) {
+	if !r.wroteHeader {
+		r.WriteHeader(http.StatusOK)
+	}
+	if !r.wroteCGIHeader {
+		r.writeCGIHeader(p)
+	}
+	return r.w.Write(p)
+}
+
+func (r *response) WriteHeader(code int) {
+	if r.wroteHeader {
+		return
+	}
+	r.wroteHeader = true
+	r.code = code
+	if code == http.StatusNotModified {
+		// Must not have body.
+		r.header.Del("Content-Type")
+		r.header.Del("Content-Length")
+		r.header.Del("Transfer-Encoding")
+	}
+	if r.header.Get("Date") == "" {
+		r.header.Set("Date", time.Now().UTC().Format(http.TimeFormat))
+	}
+}
+
+// writeCGIHeader finalizes the header sent to the client and writes it to the output.
+// p is not written by writeHeader, but is the first chunk of the body
+// that will be written. It is sniffed for a Content-Type if none is
+// set explicitly.
+func (r *response) writeCGIHeader(p []byte) {
+	if r.wroteCGIHeader {
+		return
+	}
+	r.wroteCGIHeader = true
+	fmt.Fprintf(r.w, "Status: %d %s\r\n", r.code, http.StatusText(r.code))
+	if _, hasType := r.header["Content-Type"]; r.code != http.StatusNotModified && !hasType {
+		r.header.Set("Content-Type", http.DetectContentType(p))
+	}
+	r.header.Write(r.w)
+	r.w.WriteString("\r\n")
+	r.w.Flush()
+}
+
+func (r *response) Flush() {
+	if !r.wroteHeader {
+		r.WriteHeader(http.StatusOK)
+	}
+	r.w.Flush()
+}
+
+func (r *response) Close() error {
+	r.Flush()
+	return r.w.Close()
+}
+
+type child struct {
+	conn    *conn
+	handler http.Handler
+
+	mu       sync.Mutex          // protects requests:
+	requests map[uint16]*request // keyed by request ID
+}
+
+func newChild(rwc io.ReadWriteCloser, handler http.Handler) *child {
+	return &child{
+		conn:     newConn(rwc),
+		handler:  handler,
+		requests: make(map[uint16]*request),
+	}
+}
+
+func (c *child) serve() {
+	defer c.conn.Close()
+	defer c.cleanUp()
+	var rec record
+	for {
+		if err := rec.read(c.conn.rwc); err != nil {
+			return
+		}
+		if err := c.handleRecord(&rec); err != nil {
+			return
+		}
+	}
+}
+
+var errCloseConn = errors.New("fcgi: connection should be closed")
+
+var emptyBody = io.NopCloser(strings.NewReader(""))
+
+// ErrRequestAborted is returned by Read when a handler attempts to read the
+// body of a request that has been aborted by the web server.
+var ErrRequestAborted = errors.New("fcgi: request aborted by web server")
+
+// ErrConnClosed is returned by Read when a handler attempts to read the body of
+// a request after the connection to the web server has been closed.
+var ErrConnClosed = errors.New("fcgi: connection to web server closed")
+
+func (c *child) handleRecord(rec *record) error {
+	c.mu.Lock()
+	req, ok := c.requests[rec.h.Id]
+	c.mu.Unlock()
+	if !ok && rec.h.Type != typeBeginRequest && rec.h.Type != typeGetValues {
+		// The spec says to ignore unknown request IDs.
+		return nil
+	}
+
+	switch rec.h.Type {
+	case typeBeginRequest:
+		if req != nil {
+			// The server is trying to begin a request with the same ID
+			// as an in-progress request. This is an error.
+			return errors.New("fcgi: received ID that is already in-flight")
+		}
+
+		var br beginRequest
+		if err := br.read(rec.content()); err != nil {
+			return err
+		}
+		if br.role != roleResponder {
+			c.conn.writeEndRequest(rec.h.Id, 0, statusUnknownRole)
+			return nil
+		}
+		req = newRequest(rec.h.Id, br.flags)
+		c.mu.Lock()
+		c.requests[rec.h.Id] = req
+		c.mu.Unlock()
+		return nil
+	case typeParams:
+		// NOTE(eds): Technically a key-value pair can straddle the boundary
+		// between two packets. We buffer until we've received all parameters.
+		if len(rec.content()) > 0 {
+			req.rawParams = append(req.rawParams, rec.content()...)
+			return nil
+		}
+		req.parseParams()
+		return nil
+	case typeStdin:
+		content := rec.content()
+		if req.pw == nil {
+			var body io.ReadCloser
+			if len(content) > 0 {
+				// body could be an io.LimitReader, but it shouldn't matter
+				// as long as both sides are behaving.
+				body, req.pw = io.Pipe()
+			} else {
+				body = emptyBody
+			}
+			go c.serveRequest(req, body)
+		}
+		if len(content) > 0 {
+			// TODO(eds): This blocks until the handler reads from the pipe.
+			// If the handler takes a long time, it might be a problem.
+			req.pw.Write(content)
+		} else if req.pw != nil {
+			req.pw.Close()
+		}
+		return nil
+	case typeGetValues:
+		values := map[string]string{"FCGI_MPXS_CONNS": "1"}
+		c.conn.writePairs(typeGetValuesResult, 0, values)
+		return nil
+	case typeData:
+		// If the filter role is implemented, read the data stream here.
+		return nil
+	case typeAbortRequest:
+		c.mu.Lock()
+		delete(c.requests, rec.h.Id)
+		c.mu.Unlock()
+		c.conn.writeEndRequest(rec.h.Id, 0, statusRequestComplete)
+		if req.pw != nil {
+			req.pw.CloseWithError(ErrRequestAborted)
+		}
+		if !req.keepConn {
+			// connection will close upon return
+			return errCloseConn
+		}
+		return nil
+	default:
+		b := make([]byte, 8)
+		b[0] = byte(rec.h.Type)
+		c.conn.writeRecord(typeUnknownType, 0, b)
+		return nil
+	}
+}
+
+// filterOutUsedEnvVars returns a new map of env vars without the
+// variables in the given envVars map that are read for creating each http.Request
+func filterOutUsedEnvVars(envVars map[string]string) map[string]string {
+	withoutUsedEnvVars := make(map[string]string)
+	for k, v := range envVars {
+		if addFastCGIEnvToContext(k) {
+			withoutUsedEnvVars[k] = v
+		}
+	}
+	return withoutUsedEnvVars
+}
+
+func (c *child) serveRequest(req *request, body io.ReadCloser) {
+	r := newResponse(c, req)
+	httpReq, err := cgi.RequestFromMap(req.params)
+	if err != nil {
+		// there was an error reading the request
+		r.WriteHeader(http.StatusInternalServerError)
+		c.conn.writeRecord(typeStderr, req.reqId, []byte(err.Error()))
+	} else {
+		httpReq.Body = body
+		withoutUsedEnvVars := filterOutUsedEnvVars(req.params)
+		envVarCtx := context.WithValue(httpReq.Context(), envVarsContextKey{}, withoutUsedEnvVars)
+		httpReq = httpReq.WithContext(envVarCtx)
+		c.handler.ServeHTTP(r, httpReq)
+	}
+	// Make sure we serve something even if nothing was written to r
+	r.Write(nil)
+	r.Close()
+	c.mu.Lock()
+	delete(c.requests, req.reqId)
+	c.mu.Unlock()
+	c.conn.writeEndRequest(req.reqId, 0, statusRequestComplete)
+
+	// Consume the entire body, so the host isn't still writing to
+	// us when we close the socket below in the !keepConn case,
+	// otherwise we'd send a RST. (golang.org/issue/4183)
+	// TODO(bradfitz): also bound this copy in time. Or send
+	// some sort of abort request to the host, so the host
+	// can properly cut off the client sending all the data.
+	// For now just bound it a little and
+	io.CopyN(io.Discard, body, 100<<20)
+	body.Close()
+
+	if !req.keepConn {
+		c.conn.Close()
+	}
+}
+
+func (c *child) cleanUp() {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	for _, req := range c.requests {
+		if req.pw != nil {
+			// race with call to Close in c.serveRequest doesn't matter because
+			// Pipe(Reader|Writer).Close are idempotent
+			req.pw.CloseWithError(ErrConnClosed)
+		}
+	}
+}
+
+// Serve accepts incoming FastCGI connections on the listener l, creating a new
+// goroutine for each. The goroutine reads requests and then calls handler
+// to reply to them.
+// If l is nil, Serve accepts connections from os.Stdin.
+// If handler is nil, http.DefaultServeMux is used.
+func Serve(l net.Listener, handler http.Handler) error {
+	if l == nil {
+		var err error
+		l, err = net.FileListener(os.Stdin)
+		if err != nil {
+			return err
+		}
+		defer l.Close()
+	}
+	if handler == nil {
+		handler = http.DefaultServeMux
+	}
+	for {
+		rw, err := l.Accept()
+		if err != nil {
+			return err
+		}
+		c := newChild(rw, handler)
+		go c.serve()
+	}
+}
+
+// ProcessEnv returns FastCGI environment variables associated with the request r
+// for which no effort was made to be included in the request itself - the data
+// is hidden in the request's context. As an example, if REMOTE_USER is set for a
+// request, it will not be found anywhere in r, but it will be included in
+// ProcessEnv's response (via r's context).
+func ProcessEnv(r *http.Request) map[string]string {
+	env, _ := r.Context().Value(envVarsContextKey{}).(map[string]string)
+	return env
+}
+
+// addFastCGIEnvToContext reports whether to include the FastCGI environment variable s
+// in the http.Request.Context, accessible via ProcessEnv.
+func addFastCGIEnvToContext(s string) bool {
+	// Exclude things supported by net/http natively:
+	switch s {
+	case "CONTENT_LENGTH", "CONTENT_TYPE", "HTTPS",
+		"PATH_INFO", "QUERY_STRING", "REMOTE_ADDR",
+		"REMOTE_HOST", "REMOTE_PORT", "REQUEST_METHOD",
+		"REQUEST_URI", "SCRIPT_NAME", "SERVER_PROTOCOL":
+		return false
+	}
+	if strings.HasPrefix(s, "HTTP_") {
+		return false
+	}
+	// Explicitly include FastCGI-specific things.
+	// This list is redundant with the default "return true" below.
+	// Consider this documentation of the sorts of things we expect
+	// to maybe see.
+	switch s {
+	case "REMOTE_USER":
+		return true
+	}
+	// Unknown, so include it to be safe.
+	return true
+}